A conventional automatic paper-feeding mechanism applied in machines like printers, scanners, copiers, or fax machines generally adopt the unidirectional torsion spring type or the electronic clutch type of control action for a paper-in roller thereof to accomplish the object of automatic paper feeding.
FIG. 1 shows a conventional unidirectional torsion spring type automatic paper-feeding mechanism, wherein an upper-tight-lower-loose unidirectional torsion spring 11a and an upper-loose-lower-tight unidirectional torsion spring 12a are slipped onto two ends of a pivot 10a, respectively. The two torsion springs 11a and 12a of opposite attributes are used to keep a constant friction force, and forward and reverse rotations of a motor are matched to control upward and downward paper-feeding actions of a paper-in roller 1a. However, because the two unidirectional torsion springs 11a and 12a are used to control the paper-feeding action of the paper-in roller 1a, when the unidirectional torsion spring type automatic paper-feeding mechanism feeds a paper in, the paper-in roller 1a cannot be lifted. Therefore, the friction between the paper-in roller 1a and the machine body will increase the load after the tail end of the paper leaves the paper-in roller 1a, hence causing jiggle of paper to affect its image quality.
FIG. 2 shows a conventional electronic clutch type automatic paper-feeding mechanism, wherein attraction and release actions of an electronic clutch 2a matched with containment of an elastic component 20a are exploited to control paper-leading actions like downward pressing or upward raising of a paper-in roller. However, the required cost of this type is too high. Moreover, because the control can only be accomplished with circuits, its internal circuit layout will be very complicated.
Furthermore, in a common automatic paper-feeding mechanism, special low-abrasion or abrasion-resistant material must be padded to avoid deterioration of image quality due to difference of load when the paper-in roller acts again after a paper is sent out. However, this special low-abrasion or abrasion-resistant material will further result in increase of the cost.
Accordingly, the above two conventional automatic paper-feeding mechanisms have drawbacks and inconvenience in practical use. The present invention aims to resolve the problems in the prior art.